class into another, and marks of distinction which have become articles of faith lose their individual reality. We have now mammals which lay eggs and, if the news is established, birds also which go on all fours. It was already observed, before the time of Virchow, as a conclusion of the discovery of the cell, that the identity of the individual creature is lost, scientifically and dialectically speaking, in a federation of cells, so the idea of animal (and therefore human) individuality is still further complicated by the discovery of the amoeba in the bodies of the higher animals constituting the white blood corpuscles. And these are just the things which were considered polar opposites, irreconcilable and insoluble, the fixed boundaries and differences of classification, which have given modern theoretical science its limited and metaphysical character. The knowledge that these distinctions and antagonisms actually do occur in nature, but only relatively, and that on the other hand that fixity and absoluteness are the products of our own minds--this knowledge constitutes the kernel of the dialectic view of nature. The view is reached under the compulsion of the mass of scientific facts, and one reaches it the more easily by bringing to the dialectic character of these facts a consciousness of the laws of dialectic thought. At all events, the scope of science is now so great that it no longer escapes the dialectic comprehension. But it will simplify the process if it is remembered that the results in which these discoveries are comprehended are ideas, that the art of operating with ideas is not inborn, moreover, and is not vouchsafed every day to the ordinary mind, but requires actual thought, and this thought has a long history crammed with experiences, neither more nor less than the accumulated experiences of investigation into nature. By these means, then, it learns how to appropriate the results of fifteen hundred years development of philosophy, it gets rid of any separate natural philosophy which stands above or alongside of it and the limited method of thought brought over from English empiricism. _London, 22nd September, 1885._ III